Almost every overflowing gutter comes down to one of seven causes. On Chicago’s North Shore it is usually one of the first two: a clogged gutter, or a clogged downspout hidden below it. The table below matches what you are seeing to the likely cause.
Which One Do You Have?
Match what you are seeing to the most likely cause. Each row links to the full explanation.
| What you are seeing | Most likely cause | Typical fix |
|---|---|---|
| Water spills along the whole run | Clogged gutters | Full cleaning, from $150 |
| Water spills at one corner or one end, the rest drains fine | Clogged downspout or buried drain line | Downspout cleared with a cleaning; buried drain from $95 |
| Gutters are clean but still holding water a day after rain | Wrong slope | Re-pitch the run, from $75 |
| Overflow only in the heaviest rain, gutters are clean | Undersized gutters or too few downspouts | Add a downspout, from $150 |
| You can see the gutter dipping or leaning from the street | Sagging hangers | Re-secure and re-pitch, from $75 |
| Water shoots past the gutter where two roof sections meet | Roof-valley overshoot | Splash guard, $100 |
| Water runs behind the gutter and down the fascia or siding | Missing or short drip edge | Quoted at inspection |
The sections below take each cause in turn, with how to confirm it on your own house and what the fix involves. If water is coming over the edge right now, call 847-230-7447, since same-day service is available.
The 7 Reasons Gutters Overflow
Start at the top of this list. In our experience the first two causes explain most overflowing gutters, and they are also the cheapest to fix.
1Clogged gutters
Leaves, seed pods, and shingle grit pile up in the channel until water has nowhere to go but over the edge. You will see it spill along a whole run, or spot plants sprouting from the trough.
The fix is a full cleaning, with every run cleared and the debris hauled away. Gutter cleaning starts at $150 for a one-story home, and the price is confirmed before any work begins.
2Clogged downspouts or buried drain lines
The gutter looks clear from the ground, but the downspout outlet is plugged with wet leaf sludge, so the whole run backs up and spills. Buried extensions clog too, especially where they meet a French drain.
The overflow concentrates near one corner while the rest of the run drains fine, or a downspout goes quiet during heavy rain.
The fix: clear the outlet and flush the downspout with water until flow is confirmed. We do this on every visit, and clogged downspouts are cleared at no extra charge as part of a standard gutter cleaning. A buried drain line is the exception, since clearing a French drain is separate work at $95 for the first drain and $70 for each additional one.
3Wrong slope
Gutters need about a quarter inch of fall for every 10 feet toward the downspout. A flat or back-tilted section lets water pool and slop over instead of draining.
Water that sits in the trough instead of moving toward the downspout is the giveaway. We correct the slope from $75 during the same visit.
4Undersized gutters or too few downspouts
A large roof draining through a single 5-inch gutter and one downspout will overflow in a downpour no matter how clean it is. One downspout per 30 to 40 feet of gutter is usually needed, so pace off your runs and count.
If overflow only happens in the hardest rain and the gutters are spotless, capacity is the likely culprit. We add a downspout from $150, or scope a larger gutter during an inspection.
5Sagging or loose hangers
When hangers pull away from the fascia, the gutter tilts forward and water sheets over the front lip. You can usually see the dip from the street.
We re-secure and re-pitch a sagging run from $75. A badly bent section needs replacing instead.
6Roof-valley overshoot
Where two roof planes meet, rain concentrates into a fast channel that can jump straight over the gutter below. The gutter passes every other test, and water still lands on your patio. A splash guard at the valley mouth solves it, installed at $100.
7Missing drip edge
A drip edge, or the wider version of it called a gutter apron, is the metal flashing that carries water off the shingles and into the trough. Without one, or when the shingles do not overhang far enough, water wicks backward off the shingle edge instead of falling into the gutter.
Look for staining or peeling paint on the fascia behind the gutter, with water running down the siding while the gutter itself stays clean.
The fix depends on how the roof edge is built, so we quote this one at inspection rather than off a price list.
Why North Shore Gutters Overflow on a Schedule
Around Northbrook, Glenview, Highland Park, Wilmette, and Winnetka, most homes sit under mature oaks, maples, and pines, and those trees put gutters on a calendar.
Spring brings maple seeds and pollen that pack down into a waterproof plug.
Then comes the cottonwood, from about mid-May through early June. Cottonwood fluff looks harmless drifting across a yard. In a gutter it wets down and mats into a felt layer that water runs over instead of through.
It is easy to miss, and it arrives right before the summer storm season.
Every fall we give North Shore homeowners the same timing advice. Wait until the oaks finish dropping before the final cleaning, since mature oaks here hold their leaves late.
Gutters cleaned in early October are often full again by Thanksgiving. A cleaning in late November is worth more than one in September.
Ice dams are what an unfixed clog turns into
A gutter clogs during the November leaf drop, holds water instead of draining, and that water freezes.
Snow on the roof then melts from below, where the attic is warm, and runs down to the cold roof edge. There it meets a gutter that is already solid ice.
The meltwater has nowhere to go, so it backs up under the shingles and finds the fascia, the soffit, or the ceiling below.
The overflow you are watching in July is the same clog that becomes an ice dam in January. It is cheapest to fix now.
Overflowing Even Though the Gutters Look Clean?
A single rainstorm usually shows which one it is.
During the next rain, watch the downspout where it meets the ground. Strong flow there means the system is draining and the problem is capacity or overshoot. Weak flow means a plug somewhere between the outlet and the ground, often in a buried extension you cannot see.
With no rain in the forecast, check for standing water instead. Water still sitting in a clean gutter points to slope rather than debris.
“Professional and efficient. Their pricing was clearly explained and the gentleman cleaning brought my attention to a downspout issue I was unaware of. I will continue to use Sparkle’s services.”
Jorge A. · Northbrook
A real job: Winnetka, July 2026
A Winnetka homeowner called about water coming over the gutters in rain. The gutters looked clean from the ground, and from the roof they looked clean too.
Ivan P. found the cause once he checked flow. Every downspout on the house was plugged. Water had nowhere to go, so the runs held standing water and spilled over the front edge instead of draining.
The crew cleaned the gutters, cleared each downspout, and flushed the system with water until flow was confirmed at the ground.
| Home | 2-story, about 2,900 sq ft |
| Date | July 8, 2026 |
| Cause | Clogged downspouts on every run |
| Price | $210 |
Gutter cleaning is priced in size bands rather than by the foot, so homes across a range of square footage land at the same number.
“Sparkle has done our gutters multiple times. They are so easy to deal with. Also they do a fantastic job at a reasonable price.”
Patrick D. · Winnetka
Homes under mature trees usually need this more than once a year. Our service plans cover scheduled cleanings so downspouts get flushed before they back up.
Gutter Guards Can Cause Overflow Too
We install gutter guards, and good micro-mesh guards genuinely cut down how often you need a cleaning. They also cost more to clean around: guards have to come off and go back on to reach the trough, so plastic guards add 35% to a cleaning and aluminum guards add 50%.
But guards can also cause overflow. Fine mesh can sheet fast rain straight past the gutter, and debris mats on top of cheap covers instead of washing off. In winter, guards ice over.
If your overflow started after guards went on, check the guards first.
What Overflow Does If You Ignore It
An overflowing gutter drops roof runoff along the foundation, which is the one place you do not want it. First it shows up as stained siding and rotted fascia. Then it shows up in the basement.
Water damage is not a rare problem. About one in 60 insured homes files a water damage or freezing claim in a given year, and those claims average nearly $14,000, according to industry data published by the Insurance Information Institute.
Here is the part most homeowners do not learn until they file. Standard homeowners policies cover water damage that is sudden and accidental.
They generally exclude two things that describe gutter overflow exactly: damage caused by lack of maintenance, and groundwater entering through basement walls and floors. An adjuster who traces a wet basement back to gutters that sat full for two seasons is looking at both exclusions at once.
Coverage varies, so read your own policy. Just do not assume the repair gets paid for.
That is the real math on an overflowing gutter. A cleaning is a scheduled cost you control, and the repair is neither.
Most causes on this page are fixed for somewhere between nothing and the price of a standard cleaning.
Overflowing Gutter Questions
How do I stop my gutters from overflowing?
Start with a full cleaning that includes flushing every downspout, since clogs cause most overflow. If cleaning does not stop it, check slope, hanger tightness, and capacity, in that order. Those three cover nearly every remaining case.
Is it normal for gutters to overflow in heavy rain?
A brief spill during the hardest minutes of a downpour can be normal, especially at roof valleys. Overflow that starts early in a storm, or happens in ordinary rain, is not normal and usually means a clog or slope problem.
Why are my gutters overflowing but not clogged?
Most often a plugged downspout or buried drain line, invisible from the ground. Wrong slope, undersized capacity, and a missing drip edge are the others to check.
The downspout test during rain tells you which. Strong flow at the ground means capacity or overshoot, weak flow means a hidden plug.
Can overflowing gutters leak into the house?
Yes, two ways. Water running down the wall can find gaps around windows and siding, and in winter an iced-over clog can push meltwater under the shingles and into ceilings. Both start as an overflow problem you can see from the yard.
Water Coming Over the Edge Right Now?
We clean and flush gutters across the North Shore, with same-day service available. Call 847-230-7447, or get a starting price from the calculator on our gutter cleaning page.
For the full price breakdown, see what gutter cleaning costs.